Measurements of the ablation-front trajectory and low-mode nonuniformity in direct-drive implosions using x-ray self-emission shadowgraphy. (2015)

• Record Type: Journal Article
• Authors: Michel, D.T.; Davis, A.K.; Armstrong, W.; Bahr, R.; Epstein, R.; Goncharov, V.N.; Hohenberger, M.; Igumenshchev, I.V.; Jungquist, R.; Meyerhofer, D.D.; Radha, P.B.; Sangster, T.C.; Sorce, C.; Froula, D.H.
• Is Part Of: High power laser science and engineering. Volume 3(2015)
• Publication Date: 2015
• Subjects: low mode nonuiformity, -- nuclear fusion, -- self-emission shadowgraphy, -- shell trajectory; High power lasers -- Periodicals; 621.366
• DOI: 10.1017/hpl.2015.15
• Languages: English
• ISSNs: 2095-4719

Abstract

Abstract : Self-emission x-ray shadowgraphy provides a method to measure the ablation-front trajectory and low-mode nonuniformity of a target imploded by directly illuminating a fusion capsule with laser beams. The technique uses time-resolved images of soft x-rays ( ${>}1$ keV) emitted from the coronal plasma of the target imaged onto an x-ray framing camera to determine the position of the ablation front. Methods used to accurately measure the ablation-front radius ( ${\it\delta}R=\pm 1.15~{\rm\mu}\text{m}$ ), image-to-image timing ( ${\it\delta}({\rm\Delta}t)=\pm 2.5$ ps) and absolute timing ( ${\it\delta}t=\pm 10$ ps) are presented. Angular averaging of the images provides an average radius measurement of ${\it\delta}(R_{\text{av}})=\pm 0.15~{\rm\mu}\text{m}$ and an error in velocity of ${\it\delta}V/V=\pm 3\%$ . This technique was applied on the Omega Laser Facility [Boehly et al., Opt. Commun.133, 495 (1997)] and the National Ignition Facility [Campbell and Hogan, Plasma Phys. Control. Fusion41, B39 (1999)].